Our invention relates to apparatus employing disklike record media for the recording and/or reproduction of information, and more specifically to a data transfer system of the type comprising a plurality of daisy chained disk drives or files for selective data transfer to or from several record disks. Our invention has particular utility in conjunction with flexible magnetic disks known also as floppy disks, although we do not wish our invention to be unnecessarily limited thereto.
Flexible magnetic disks have found widespread acceptance in information processing and allied industries as compact data storage media. Being thin and limply flexible, the disks are commonly enclosed in more rigid, apertured envelopes to make up disk assemblies or cartridges that are self supporting. A variety of disk files or drives have been suggested and used for data transfer to and from such disk cartridges. Dalziel et al. U.S. Pat. No. 3,678,481 and Castrodale et al. U.S. Pat. No. 4,089,029 disclose examples of such known devices.
It has also been known to "daisy chain" a plurality of such disk files to a central processing unit (CPU) via a controller, with the disk files in parallel relation to each other, for selective use of the magnetic disks in the files. In a typical conventional data storage system comprising a group of daisy chained disk files (see FIG. 1 of the drawings attached hereto), the controller applies a common MOTOR ON signal to the motor drive circuits of all the files. The MOTOR ON signal sets all the disk drive motors into rotation, regardless of whether each file is being used for data tranfer or not. This of course incurs a substantial waste of electrical energy and shortens the useful life of the disk drives. It might be contemplated to rotate each disk drive motor only when the associated disk is actually required for data storage or readout. This solution would necessitate a sacrifice in accessibility, however, as the motors on energization require a considerable length of time to pick up speed and start rotation at a required constant rate.